Arrhythmias

Cardiovascular course 4th year - Pathophysiology

Arrhythmias - Definition and Causes

• Abnormal rhythm of the heart• Causes

1. Abnormal rhythmicity of the pacemaker (tachycardia, bradycardia)2. Shift of the pacemaker to another place in the heart (junctional.

Idioventricular rhythms)3. Block of different parts of the conducting system (impulse conduction

blocks)4. Abnormal pathway of impulses transmission (WPW syndrome)5. Spontaneous generation of impulses in atrias or ventricles (premature

beats, paroxysmal tachycardia, fibrillation, flutter)6. Ionic dysbalance (changes of depolarisation, repolarisation)

Mechanisms of Cardiac Arrhythmias

Mechanisms of bradycardias

Mechanisms generating tachycardias • Accelerated automaticity •Triggered activity•Re-entry

Mechanisms of bradycardias

Mechanisms generating tachycardias • Accelerated automaticity •Triggered activity•Re-entry

Abnormal Sinus Rhythms

abnormal rhythmicity of the pacemaker

Tachycardia

Bradycardia

• Extrinsic causes Intrinsic causes

Impulse Conduction Block Sinoatrial blockSinus Arrest

Atrioventricular blockblock between atrias and ventricles

Interventricular block ( RBBB or LBBB)impulses fail to reach part of the heart during heart cycle

Types of AV Blocks1st degree

2nd degree block: partial block

Mobitz IMobitz I

3rd degree block: complete heart block

Right and Left Bundle Branch Blocks

Right bundle branch block (RBBB)

Left bundle branch block (LBBB)

Preexcitation Syndrome – Wolff-Parkinson-White

• AV conduction through the accessory pathway is faster than through the AV node

Premature Beats - Extrasystoles• the heart beats before the time of normal contraction.

Types:• Premature atrial contraction• Premature junctional contraction• Premature ventricular contraction

Paroxysmal Tachycardia

• rapid rhythmical discharge of impulses that spread throughout the heart• caused by re-entrant circuitry movement• Types of paroxysmal tachycardia

– Paroxysmal supraventricular tachycardia (atrial, junctional)– Paroxysmal ventricular tachycardia

Fibrillation• results from cardiac impulses that have gone chaotically within the muscle• known as a phenomenon of re-entry:

Types:• atrial• ventricular

Atrial Flutter• atrial focus activates the atria at a rate of around 300 times per minute

A Systematic Approach to Reading the 12-lead ECG Check these data (patient’s name, birthday, and identification number; date and time of tracing) on the ECG to make sure:

– It belongs to the patient you are reviewing. – It was obtained on the day and time you requested the examination.

• Review the patient’s medical history, physical and laboratory findings, diagnosis, and indication of the ECG examination. You still should review all aspects of the ECG before drawing your conclusion.• Make old tracings available for comparison. In medical practice, changes in findings over time are as important as the presence or absence of findings at any discrete moment in time.• Check heart rate.• Check rhythm:

– Primary rhythm: supraventricular (sinus, atrial, junctional) or ventricular in origin.– Superimposed abnormalities (escape or premature beats).

• Check heart blocks.• Check QRS axis.

– Enlargement of right and left ventricle– Bundle braches blocks

• Check signs of clinical abnormalities:– Right and left atrial abnormalities.– Right and left ventricular hypertrophy.– Right and left bundle branch block.– Acute myocardial infarction.– Electrolyte abnormalities.– Drug effects.– Pulmonary embolism.

• Correlate the ECG findings with the patient’s clinical presentation. Treat the patient; not the waveforms.